Thinking about adding a (?hydraulic?) thumb to my full size backhoe

[Piston]

In my quest to make my backhoe more useful, I'm thinking about adding a thumb to it.

I added a grapple to my tractor and it was the best thing I've ever done! I can only imagine I'll get a similar feeling with the backhoe. The backhoe in question is an older John Deere 410B, not sure of the year, maybe a 1985, it has a bit over 4,000hrs on it and I'm sure it has a lot of life left in it, as long as I keep using it and don't let it sit and go unused! The more useful it is of course, the more I'll use it :thumbsup:

A quick little rundown on my idea. I work away from home and we have a lot of scrap steel where I work. I can pretty much build the thing with steel that we would otherwise throw away to the scrap bin, plus we have tools at work that I can use that aren't available to me at home. I've checked with my supervisor to make sure it's okay to do this, and he's given me the okay.

The problem is, I have to ship it home! I estimate it will weigh around 250 lbs by the time I'm done with it. So my plan is to design the thumb using Sketchup, then break it into individual pieces in the drawing, and cut/fit all the pieces, but not weld them. Once I get it home, I will weld it all together.

Not sure if this is going to work or not, but I'm gonna give it a shot (pending one more "okay" from work to use the scrap materials).

I've been looking online at pics and came up with a general sketch of what I'd like, as well as size. I'll post the Sketchup drawing once I get a little more 'finished' with it.

The more I mess with the Sketchup drawing, the more I think about making the thumb hydraulic. I'm curious if someone could give me a very quick and basic rundown on the differences of adding a selector valve to a closed center system, vs an open center system? I've become semi familiar with adding hydraulics to my tractor, (link in my sig) and I feel I could pretty easily do it to the backhoe to, if it isn't much different. I'm not sure about the cost yet though, that will have to be figured once I figure out what the heck I even need :laughing:

Here are a couple pics of the backhoe I will (hopefully) have a thumb for someday. This may be a long drawn out process, and in fact there is a good chance it won't happen at all, but I figure if I post up on here, I'll have more pressure to get it done :laughing:

 

[boggen]

be careful on your measurements. with how everything is large then gets smaller towards the bucket. for the "frame" for the thumb.

see if your tractor has an option for "extend a hoe" if so, you might be able to just pickup up the foot peddle or lever or kit. and have everything ready to go. just be careful you may have some problems trying to tie into one of the lines. to run and another hyd valve.

open center system is what i have on 555c TLB. and hydruailc oil goes through all the levers, when the levers are in middle position (neutral). other words hyd oil is pumped through all levers all the time.

close center system. may need an actual lever to be "moved" for hyd oil to flow through the levers. (oil is only moved when it is needed)???

i may be completely off on above. been some times since i looked up info myself.

 

[Piston]

be careful on your measurements. with how everything is large then gets smaller towards the bucket. for the "frame" for the thumb.

I am waiting for a measurement from my father as I do need the inside width of the dipperstick. For now, I am making the main mounting plate 5" wide, or at least that is what it is in my model. The top, is slightly wider at 6", only to accomodate the larger size of the crosstube on the hydraulic cylinder I would go with.

I am building it with all the specs for a hydraulic setup, then, I will modify it to be a manual thumb by simply adding one more bracket a bit lower on the mounting plate, plus of course some sort of stiff arm to hold the thumb at the proper angle. The reason for this is so if I decide to make it hydraulic, it will simply be a matter of buying a hydraulic cylinder and pinning it in...well, minus all that plumbing of course :laughing:

Here is what I have so far.
The cylinder I'm planning for is 3" bore with 1 3/4" rod diameter. Fully retracted it is 28" and extended of course is 48". This will give me a full range of motion through 135 degrees.
Here is one cylinder that I found that met my specs....
https://www.surpluscenter.com/item.asp?item=9-7712-20&catname=hydraulic

All steel is 3/4" thick.

 

[Piston]

see if your tractor has an option for "extend a hoe" if so, you might be able to just pickup up the foot peddle or lever or kit. and have everything ready to go. just be careful you may have some problems trying to tie into one of the lines. to run and another hyd valve.

Looking at the specs (http://www.deere.com/en_US/docs/construction/non_current_products/backhoes/410B.pdf) It looks like there was an option for the "extendahoe" however, I don't have that option.

I was hoping I may be able to add a selector valve to another circuit, possibly an outrigger or something.

As a side note, I probably should have put this in the 'build it yourself' section

 

[J_J]

Can you verify that your BH is closed center hyd?

You should be able you tap into a closed center hyd circuit since all components are in parallel, just add another valve to the supply line/pressure hose and connect the tank line to any other tank line.

The pump flow will be divided between the valves in use.

You can use any open center valve with the closed center option that meets the pressure requirements.

Here is your thumb control. just order the valve with the closed center plug.

http://www.surpluscenter.com/item.asp?item=9-7861&catname=hydraulic

If you need a larger GPM valve this would be the one.

http://www.surpluscenter.com/item.asp?item=9-7974&catname=hydraulic

Closed center data:

http://www.engineersedge.com/hydraulic/fixed_displacment_closed_center_system.htm

 

[Piston]

Can you verify that your BH is closed center hyd?

Yes, According to the spec sheet I linked to, it is closed center hydraulics with 2500psi constant pressure and 30gpm variable flow.

You should be able you tap into a closed center hyd circuit since all components are in parallel, just add another valve to the supply line/pressure hose and connect the tank line to any other tank line.

The pump flow will be divided between the valves in use.

You can use any open center valve with the closed center option that meets the pressure requirements.

Here is your thumb control. just order the valve with the closed center plug.

Surplus Center - 1 SPOOL 8 GPM PRINCE MB11B5C1 DA VALVE

If you need a larger GPM valve this would be the one.

Surplus Center - 1 SPOOL 14 GPM PRINCE WVS11B5C1 DA VALVE

So just to make sure I understand this correctly, I can basically Tee into the supply and return lines?
So I would find my supply line, tee into that with a new supply line to my new valve, then I would simply tee into a return line with my new return line going from the new valve to the tee?
That seems too easy :laughing:

I suppose I would need a considerably larger valve but I get the idea, thanks for posting those links.

Thanks for the link to the closed center data.

 

[J_J]

Here is a 30 gal valve.

Surplus Center - 1 SPOOL 30 GPM PRINCE RD512CA5A4B1 OC VALVE

Surplus Center - CLOSED CENTER PLUG PRINCE RD5000 VALVES 660312005

I am not even sure if you need a large valve in the closed center system.

Each valve in the parallel circuit might use the volume it needs and the pump goes to rest or unloads when the demand is satisfied.

A lot of closed center use a variable speed/volume pump .

 

[Piston]

Your probably right, I guess there is no need to have the full 30gpm applied to the thumb. It's the pressure that creates the force right? So the only difference with decreased flow is that it wouldn't be able to be operated as fast?
Of course, with a thumb this wouldn't matter anyways.

What about an electric diverter valve? Could I use something like this
Surplus Center - SAE 8 15 GPM DOUBLE SELECTOR VALVE 12 VDC P15544-1
and tie into my outrigger valve?
You can see from this pic that my outrigger valve handles are in a convenient spot to operate when facing backwards using the backhoe (to the left of the operator seat when facing the backhoe.

 

[Piston]

I got the new measurements for the backhoe that I needed. The distance from the inside of the dipperstick, to the tip of the bucket teeth (with bucket at 90 degrees out) is 36".
The distance from the bottom of the dipperstick, to the top of the dipperstick, is 57 1/2". This is the face of the dipperstick that I will mount the thumb plate to.
The width of the inside of the dipperstick, is 5" at the bottom, and tapering out to 7" at the top.

I know these numbers don't seem to mean much now, but the will as the build gets going. I am mostly writing them down here so I don't lose/forget what they are later. :laughing:

 

[J_J]

Should work.

Here is the circuit diagram for the valve you posted.

http://www.surpluscenter.com/Instruct/I9-5117.pdf